The present inVention relates generally to chemical suits, and more specifically to liners therefore, and method of making same.
Chemical suits have long been worn by persons who in the course of their work may be exposed to harmful chemical vapors, liquids and gasses. Suits of this type are worn by personnel to absorb, protect and repel harmful gaseous vapors from reaching the wearer's body. Such suits are frequently worn by military personnel and other non-military personnel who may be exposed to such vapors, such as personnel who may be employed in a clean-up capacity after chemical explosions, gas leaks, etc., where harmful vapors and fumes may exist.
A conventional chemical suit comprises a garment that completely covers the wearer's person, said garment having a liner consisting of a fabric layer having a foam backing bonded thereto. When the liner is secured to the inside of the garment, the fabric layer comprises the inner surface of the garment, i.e. in contact with the wearer, with the foam backing located intermediate the fabric and the shell of the garment. For purposes of comfort, the fabric layer is conventionally an air permeable fabric, such as a nylon tricot, and the foam backing is flame-laminable polyurethane. The chemical with which the foam backing is impregnated preferably is an activated carbon, and it is the loading or filling of the foam material with the carbon that prevents penetration therethrough of harmful gaseous vapors. It is therefore critical that sufficient carbon be present throughout the lining in order to achieve complete and effective protection for the wearer. Since the chemical with which the foam is impregnated is rendered substantially ineffective by the presence of moisture, the outer garment shell is of a water-repellent material.
In the manufacture of chemical suit liners of the type above described, i.e. liners comprising an air permeable fabric layer having bonded thereto a foam backing impregnated with a suitable protective chemical, such as activated carbon, it has been found that the weight and density of the foam layer must be maintained above a predetermined minimum level in order to insure sufficient pickup or loading of the protective chemical therein. Expressed differently, if at any locations the foam backing is too porous, i.e. does not have sufficient weight and density, then at those locations an insufficient amount of the protective chemical will be picked up by the foam, thus rendering the liner ineffective for its intended purpose at those locations. This is particularly true since the foam backing is necessarily quite thin in order that the suit will not be too bulky so as to unnecessarily inhibit movement of the wearer, it being noted that the foam backing is normally in the approximate range of one-tenth of an inch in thickness. The problem that exists, however, is that the cellular structure of foams of polyurethane and the like are never uniform, since thin foam layers of this type are traditionally made by the peeling of round buns of such foam, as a result of which the peeling machine that cuts the thin foam sheet from the bun may at certain spaced intervals cut into the cellular interior of the foam in such a way that the porosity of the foam at that particular location may be relatively high. This phenomena is known in the foam industry as "banding" and since one never knows when or where in the elongated foam strip such "banding" will exist, it becomes incumbent on the manufacturers of chemical suit liners to carefully test the foam throughout its length in order to locate and eliminate those areas of the foam, or if preferable, to carefully test the completed lining in order to locate and eliminate areas that do not meet minimum protective standards. This obviously requires expensive and time-consuming testing procedures, and results in a higher percentage rejection rate of the liners than is desirable.
The present invention overcomes the problems that result from the above-discussed "banding" phenomena that inherently exists in the manufacture of elongated sheet foam, thus providing a foam backing wherein the possibility of areas thereof having insufficient density and weight is tremendously minimized. This is done by making the foam backing of a plurality of discreet layers, preferably two, which layers are laminated to each other to form the backing, which backing is then bonded to the fabric layer. Since the so-called "banding" in the elongated foam sheeting exists at widely spaced intervals, it will be understood that if the foam backing is made of two layers rather than one, at those areas where "banding" exists, such "banding" will exist in only one-half the thickness of the backing, and since the other half will possess greater weight and density, the overall backing, even at those areas, will possess sufficient weight and density so as to result in sufficient loading or pickup of the protective chemical. The separate foam layers are preferably of a thickness approximately one-half the thickness of the conventional one-layer foam backing, or perhaps slightly greater, it only being important that the thickness of the combined layers not exceed the thickness specification for liners of this type. In the manufacture of the liner of the present invention, a single foam layer may be bonded to the fabric layer and then the second foam layer laminated to the first one. Alternatively, the two foam layers may be laminated to each other to form the backing, and then the backing may be bonded to the fabric layer, or it may be preferable to make the lining in a single pass, i.e. by simultaneously laminating the two foam layers to each other, and at the same time bonding the laminated backing to the fabric layer. In each case, the impregnation of the liner with the protective chemical takes place after the foam backing has been bonded to the fabric layer.
It is therefore an object of the present invention to provide a liner for chemical suits wherein little likelihood exists that any portions of the liner do not meet required protective standards.
Another object is the provision of a liner for chemical suits wherein the foam backing thereof is constructed of a plurality of discreet foam layers that are laminated to each other.
Another object is the provision of a liner for chemical suits wherein the construction of the liner and the method of making same requires less extensive testing and minimizes the rejection rate of the liner.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.